Aviation safety investigations & reports

British Aerospace Plc BAe 146-300, VH-EWR

Summary

The BAe146 and the SAAB 340B were on converging tracks. The air
traffic controller responsible for their separation received an
electronically generated Short Term Conflict Alert (STCA) on his
display. The STCA was a warning to the controller that the
predicted radar paths of the two aircraft may lead to a loss of
separation standards. The required separation standard was 5 NM
laterally or 1,000 ft vertically. By the time the controller took
positive control and instructed the crew of the BAe146 to turn left
for avoiding action, lateral separation had reduced to below the
required standard. The crew of the SAAB received a Traffic Alert
from their aircraft's traffic alert and collision avoidance system
(TCAS).

Analysis of the radar data indicated that lateral separation
between the two aircraft reduced to 2.4 NM and vertical separation
to 500 ft. The controller did not use any separation assurance
technique in his traffic management plan. He stated that he was
used to working in a much busier air traffic environment:
circumstances that would demand closer vigilance. At the time of
the conflict, the controller was distracted from his primary task
of providing a radar control service during a discussion with a
TAAATS Flight Data Corrections (TFDC) officer over a minor
administrative issue.